Draft: various code cleanup/API imporvements - [merged]#39

In GitLab by @artemyurchenko on Aug 17, 2020, 04:39 _Merges unify-properties-access-one-commit -> master_ - fix naming to separate public/private API (double dashes) - simplify variables manipulation with `alist-get` - store frame and tab information in variables instead of names External manipulation, such as killing is handled via listening to `kill-buffer-hook`. Renaming by user is irrelevant since we don't rely on names. Information is tied directly to the buffer object. - group code into semantically different sections - remove obsolete/redundant behaviour - move configuration procedures (such as `add-hook`) to the end of file. Otherwise, some symbols might happen to be undefined in hooked functions. - fixes #10 and #18